A spokesperson with Essentia Health Hospitals in Duluth, Minn., tells KFGO radio that Rod Bolstad of Hillsboro has been upgraded from critical to serious condition, and his son Joel has been upgraded from serious to fair condition. Another son, Jacob, remains in critical condition.

Two family friends from Fargo also remain hospitalized. Al Stokke is in fair condition and Will Huotari is in critical condition.

The men had stayed overnight in the privately owned camper-ice fishing house.

Officials say the propane furnace exploded and blew out the windows Sunday on the shore of Lake of the Woods. Authorities say they are confident the explosion was accidental.

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